The automotive industry is actively searching for measures to reduce the CO2 emission of automotive vehicles by means of power reduction in the electronics present in such vehicles. One possible area where energy consumption could be reduced is the vehicle bus communication, in which all connected electronic control modules are kept active, just because there is bus communication. It is desired to reduce the power consumption by de-activating those control units which are not needed in certain phases of vehicle operation. This requires a new operating mode for bus transceivers, which is called “Partial Networking”.
A known approach involves exchanging suitable bus messages, by means of which bus nodes such as stations that are part of a partial network can request each other to change between different states or modes of operation, particularly a sleep mode that saves energy and a normal mode that consumes more energy than the sleep mode. For example, even when the vehicle is parked, individual stations have to be woken up at regular intervals to perform individual functions. As well as it being possible for a change to be made between the sleep mode and the normal mode, it is also desirable for this change to be able to be made selectively, i.e. for individual stations to be able to be actuated separately.
Typically bus message based protocols employed in automotive vehicles are for example the CAN (controller area network) protocol or the LIN (local interconnect network) protocol or the FlexRay protocol.
The CAN protocol is designed specifically for automotive applications which may also be used in other areas such as other types of vehicles, industrial automation and medical equipment. The CAN protocol is standardized in ISO 11898-1 (2003).
Accordingly, the controller area network (CAN) or the CAN-bus allows microcontrollers to communicate with each other within a vehicle. The (bus) protocol controllers connected by the CAN-bus are exchanging typically sensor data, actuator commands, service data and the like, but other components also could be included in the network.
Automotive bus transceivers normally provide a simple interface for mode control of a microcontroller in a network. A typical standard transceiver makes use of up to two dedicated mode control pins, and this means that there are usually not more than four different states of operation.
More complex interfaces, such as that of Inter-Integrated Circuits (I2Cs) or the Serial-Parallel-Interface (SPI), are known to increase the number of control modes for a device. Also, it is known to add additional dedicated mode control pins in excess of the typical two control pins. However, in addition to the fact that these examples may provide a more expensive device, the device also is likely to be incompatible with earlier devices. This means that such a new transceiver may not be provided as a drop-in replacement for known transceivers.
WO 2006/003540 A1 describes a solution for detecting wake-up bus messages in a CAN system, in which a digital bus message on the bus system comprises at least one part that is encoded in a non-bitrate dependent manner in that the value of a bit in that part of the bus message that is encoded in a non-bitrate dependent manner is represented by the lengths of successive dominant and recessive phases of the bit stream signal on the bus line. Thereby it is possible for a transceiver to independently receive and analyze the data transmitted on the bus line and in particular, to individually wake a bus node by means of a given wake-up bus message even when the part of the bus node that is on standby at the relevant point in time does not have an accurate timer and also does not have any knowledge of the bitrate at which the data is transmitted on the bus.